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Biomedical subjects

T Wan

Publications and source records attributed to T Wan.

32 records · Page 2Linked to original sources
PubMed1996

Crystallization of a complex between the Fab fragment of a human immunoglobulin M (IgM) rheumatoid factor (RF-AN) and the Fc fragment of human IgG4.

Rheumatoid factors (RF) are the characteristic autoantibodies found in patients with rheumatoid arthritis. They recognize epitopes in the Fc region of immunoglobulin G (IgG) and are often of the IgM isotype. In order to analyse the nature of RF-Fc interactions, we have crystallized a complex between the Fab fragment of a human monoclonal IgM rheumatoid factor (RF-AN) and the Fc fragment of human IgG4. The stoichiometry of the complex within the crystals was found to be 2:1 Fab:Fc. The crystals diffracted X-rays to 0.3 nm resolution, and the space group was C2, with cell dimensions a = 16.03 nm, b = 8.19 nm, c = 6.42 nm, beta = 98.3 degrees. We have also determined the sequence of the variable region of the RF-AN light chain, not hitherto reported. This belongs to the V lambda III-a subgroup and is closely related to the germline gene Humlv318, from which it differs in three amino acid residues. This is the first reported crystallized complex between a human autoantibody and its autoantigen.

Amino Acid Sequence↗
PubMed1995

Crystallization and X-ray analysis of a single fab binding domain from protein L of Peptostreptococcus magnus.

Protein L is a multidomain cell wall constituent of certain strains of Peptostreptococcus magnus which binds to the variable domain of immunoglobulin kappa-light chains. A single immunoglobulin-binding domain of M(r) = 9000 from this protein has been isolated and crystallized. The crystals are of space group P4(2)2(1)2, with cell dimensions a = b = 66.9 A, c = 68.3 A, and diffract to at least 2.2 A resolution. The asymmetric unit of the crystal contains two molecules of the protein L domain, related by a noncrystallographic 2-fold axis, as revealed by a self-rotation function calculated with native diffraction data.

Bacterial Proteins↗
PubMed1994

Crystallization and preliminary X-ray analysis of the Fab fragment of a human monoclonal IgM rheumatoid factor (2A2).

Crystals of the Fab fragment of a human monoclonal IgM rheumatoid factor have been obtained and are suitable for X-ray structure determination. This molecule, derived from the synovial B cells of a patient with rheumatoid arthritis, is an autoantibody with specificity for IgG Fc. The crystals have space group P2(1), cell dimensions a = 69.0 A, b = 76.6 A, c = 98.8 A and beta = 90.6 degrees, and diffract to a resolution of at least 2.8 A.

Antibodies, Monoclonal↗
PubMed1994

The stability and unfolding of an IgG binding protein based upon the B domain of protein A from Staphylococcus aureus probed by tryptophan substitution and fluorescence spectroscopy.

The stability and unfolding of an immunoglobulin (Ig) G binding protein based upon the B domain of protein A (SpAB) from Staphylococcus aureus were studied by substituting tryptophan residues at strategic locations within each of the three alpha-helical regions (alpha 1-alpha 3) of the domain. The role of the C-terminal helix, alpha 3, was investigated by generating two protein constructs, one corresponding to the complete SpAB, the other lacking a part of alpha 3; the Trp substitutions were made in both one- and two-domain versions of each of these constructs. The fluorescence properties of each of the single-tryptophan mutants were studied in the native state and as a function of guanidine-HCl-mediated unfolding, and their IgG binding activities were determined by a competitive enzyme-linked immunosorbent assay. The free energies of folding and of binding to IgG for each mutant were compared with those for the native domains. The effect of each substitution upon the overall structure and upon the IgG binding interface was modelled by molecular graphics and energy minimization. These studies indicate that (i) alpha 3 contributes to the overall stability of the domain and to the formation of the IgG binding site in alpha 1 and alpha 2, and (ii) alpha 1 unfolds first, followed by alpha 2 and alpha 3 together.

Base Sequence↗
PubMed1993

Why men are interested in an evaluation for a sexual problem.

OBJECTIVE: To understand why men were interested in an evaluation of a perceived sexual problem. DESIGN: Survey. SETTING: Tertiary-referral VA Medical Center in Southeast Atlantic Region. PARTICIPANTS: Respondents from a 3% random sample of male veterans age 30-99 registered at a VA medical center with completed survey data (n = 427). MEASUREMENTS: A cross-sectional mailed survey. Independent variables included survey data related to emotional state, physical state, and/or demographic characteristics (marital status, race, and age). The dependent variable was interest in evaluation of a sexual problem. MAIN RESULTS: Measures of erectile function, libido, and orgasm, when entered sequentially as separate functional sets in a logistic regression analysis, have a statistically significant (P < 0.05) influence on interest in an evaluation of a sexual problem. After controlling for sexual function and emotional state, physical state did not add to predicting interest in an evaluation for a sexual problem. After controlling for all other covariates, those who were never married, non-white, and elderly were less interested in an evaluation for a sexual problem (P < 0.05). CONCLUSION: Age, race, and marital status, in addition to sexual function, influence male veterans' interest in seeking clinical assessment for a sexual problem.

Adult↗
PubMed1993

Treatment of 121 patients with malignant effusion due to advanced lung cancer by intrapleural transfer of autologous or allogeneic LAK cells combined with rIL-2.

Lymphocytes isolated from malignant pleural effusion in patients with advanced lung cancer or from allogeneic peripheral blood of healthy donors were induced to become LAK cells after in vitro culture with rIL-2. One hundred and twenty-one patients with malignant effusions were treated by intrapleural transfer of autologous or allogeneic LAK cells combined with rIL-2. The effusion disappeared in 71 patients (58.6%) and was significantly decreased in 45 patients (36.2%). Five patients did not respond to treatment. Tumor cells in pleural effusions disappeared or were significantly decreased in number, whereas the lymphocytes were significantly increased in number in all responders. Except for transient fever in 10 patients, no serious side effect was observed.

Adenocarcinoma↗
PubMed1989

The structure of the saccharide-binding site of concanavalin A.

A complex of concanavalin A with methyl alpha-D-mannopyranoside has been crystallized in space group P212121 with a = 123.9 A, b = 129.1 A and c = 67.5 A. X-ray diffraction intensities to 2.9 A resolution have been collected on a Xentronics/Nicolet area detector. The structure has been solved by molecular replacement where the starting model was based on refined coordinates of an I222 crystal of saccharide-free concanavalin A. The structure of the saccharide complex was refined by restrained least-squares methods to an R-factor value of 0.19. In this crystal form, the asymmetric unit contains four protein subunits, to each of which a molecule of mannoside is bound in a shallow crevice near the surface of the protein. The methyl alpha-D-mannopyranoside molecule is bound in the C1 chair conformation 8.7 A from the calcium-binding site and 12.8 A from the transition metal-binding site. A network of seven hydrogen bonds connects oxygen atoms O-3, O-4, O-5 and O-6 of the mannoside to residues Asn14, Leu99, Tyr100, Asp208 and Arg228. O-2 and O-1 of the mannoside extend into the solvent. O-2 is hydrogen-bonded through a water molecule to an adjacent asymmetric unit. O-1 is not involved in any hydrogen bond and there is no fixed position for its methyl substituent.

Binding Sites↗
PubMed1980

Recent biosynthetic studies on beta-lactam antibiotics.

Recent experimental observations on the cell-free formation of penicillins and cephalosporins in protoplast lysates from C. acremonium are described. Conversion of radiolabelled penicillin N into deacetoxycephalosporin C is described. A proposal is made about the general types of mechanism involved in these conversions.

Acremonium↗
PubMed1980

Effects and costs of day-care services for the chronically ill: a randomized experiment.

Two long-term care settings not now covered by Medicare--adult day care and homemaker services--were studied in a randomized experiment to test the effects on patient outcomes and costs of using these new services. This article reports findings for day care. Patients' physical, psychosocial and health functions were assessed quarterly, and their Medicare bill files were obtained. Medicaid data were obtained on most patients, but few used many Medicaid-covered long-term care services. Multistage analysis was performed to mitigate effects of departures from the randomized design. Day-care patients showed no benefits in physical functioning ability at the end of the study, compared with the control group. Institutionalization in skilled nursing facilities was lower for the experimental group than the control group, but the factors other than the treatment variable appeared to explain most of the variance. There was a possibility that life was extended for some day-care patients. the new services averaged $52 per day or $3,235 per year. When costs for existing Medicare services used were added, the yearly cost of the experimental group was $6,501, compared with $3,809 for the control group--an increase of $2,692 or 71 per cent.

California↗
PubMedDate not supplied

Inhibition of endometrial cancer cell lines by mifepristone (RU 486).

OBJECTIVE: To determine the role of mifepristone (RU 486) in the growth of endometrial cancer cell lines, and the mechanism associated with this regulation. METHODS: Three endometrial cancer cell lines (Hec-1A, KLE, and RL95-2) were used in this study. Growth inhibition was demonstrated by sulforhodamine B cytotoxicity assay. Mode of inhibition by RU 486 was studied by induction of DNA fragmentation. The effect of RU 486 on steady-state accumulation of the progesterone and glucocorticoid receptors (PRs and GRs, respectively) and apoptosis-associated gene products was studied by Western blotting. RESULTS: We demonstrated a dose-dependent inhibition of growth in all of the three endometrial cancer cell lines. Following treatment with 5.0 micrograms/mL of RU 486, there was 39.3%, 66.3%, and 75.5% inhibition of KLE, Hec-1A, and RL95-2 cells, respectively. Decreased expression of GR in RL95-2 (0.1-10 micrograms/mL) and in KLE cells (10 micrograms/mL) was observed. A marked decrease of PR was seen with RL95-2 cells at 10 micrograms/mL, there was no change in the KLE cells, and a dose-dependent decrease was seen with Hec-1A cells. Various levels of apoptosis were demonstrated by DNA fragmentation in all three cell lines. Of the genes associated with apoptosis, dose-dependent reduction of bax expression was demonstrated in KLE cells, while induction of WAF-1 was seen in Hec-1A and RL95-2 cells, and reduction of bcl-2 was demonstrated in RL95-2 cells. CONCLUSION: Clinically achievable doses of RU 486 inhibit endometrial cancer cell lines. The mechanism of inhibition involves apoptosis, and regulation of bax, bcl-2, and WAF-1 is demonstrated. Therapeutic application of these findings remains to be determined.

Apoptosis↗